Those skilled in the art will recognize that the radio frequency (RF) spectrum is divided into specific frequency bands where certain electronic devices typically transmit and/or receive within a certain frequency band. For example, amplitude modulated (AM) radio broadcasts are transmitted in the 300-1700 KHz frequency spectrum, and frequency modulated (FM) radio and television broadcasts are transmitted in the 50-300 MHz frequency spectrum. The specific frequency that the device is using to transmit and/or receive the signals is typically referred to as a “channel.”
Throughout the specific bands of frequencies that these devices use, there are portions of the frequency spectrum that remain un-utilized. Additionally, the use of specific channels within the frequency band can change depending on the time and/or location of the user. For example, a television or radio broadcast may only transmit a signal on a channel at certain times of the day. Similarly, the same television or radio broadcast may only transmit a signal on that channel in a particular area or region and not in another area or region.
Many differing types of algorithms can be used for sensing these unused frequencies. These algorithms include those types that sense the received data using a radiometer and coherent detectors. An example of such a method is U.S. Pat. No. 6,990,087, entitled “DYNAMIC WIRELESS RESOURCE UTILIZATION.” This reference discloses the detection of spectrum gaps or “holes” that are modeled in order to predict future opportunities for frequency re-use. However, one drawback in using these types of techniques are that the prediction apparatus can be very unpredictable or erroneous if the data is not pre-conditioned due to RF front end overload or analog-to-digital converter (ADC) saturation occurring in the receiver.
Further, determining only whether the channel is being used, without determining additional information about channel operational status can generally result in false alarms that the channel is unavailable. If only channel use is determined, whether that channel is in actual use or not, can result in a high probability of false alarms. This occurs since an “in use” determination is made disregarding whether another user may be able to co-exist with or transmit over the current user.
Therefore, the need exists to develop a system and method that includes data conditioning for improving the detection probability or opportunity to re-use a frequency on a non-interfering basis where the obtained information can reduce false alarm probability.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.